1. Field of the Invention
This invention relates to a magnetic recording medium for use in a magnetic recording apparatus or the like, and to a method for fabricating it.
2. Description of the Prior Art
Metal film media called continuous media using a ferromagnetic material such as a Co-based magnetic alloy have recently been used as magnetic recording media. However, such magnetic materials as are currently used, if formed into a thin film, do not inherently possess strong in-plane magnetic anisotropy suitable for longitudinal recording. Therefore, a non-magnetic underlayer is provided on a non-magnetic substrate, and a magnetic layer is provided on the underlayer, so as to obtain in-plane magnetic anisotropy. In these magnetic media, however, the characteristics of the magnetic layer vary with the film configuration and the status of non-magnetic underlayer. Therefore, the magnetic layer must be fabricated as carefully as the underlayer, which complicates the control of the process for fabricating the underlayer film.
On the other hand, it is known that exchange coupling between magnetized fine grains increases the magnetization transitional width and causes medium noise. In order to increase the recording density, it is important to suppress medium noise. JA PUPA 1-232516 and JA PUPA 1-23517 disclose techniques for reducing medium noise wherein a new alloy of quaternary or higher degree is prepared by adding an element or elements (C, P, Bi, and so forth) to a Co-based magnetic ternary alloy, and a film of the obtained alloy is fabricated on a substrate. However, because coupling between magnetic alloy grains remains in the magnetic layer, medium noise is not suppressed sufficiently. Further, the coercivity obtained may be less than 1000 (Oe). In addition, a Cr underlayer is still required.